Typical electronic mail (e-mail) systems utilize a mail server, typically controlled by the ISP or other manager of email service, as well as a mail client located on each user's machine. The mail server typically has permanent access to the Internet, as well as other external networks and public data communications networks. The mail server stores and manages user electronic mails. Mail for each authorized user on the system is maintained within an individual storage architecture, commonly known as an inbox. FIG. 1 is a block diagram illustrating this type of design. The mail server 100 stores incoming emails, and then is periodically polled by one or more mail clients 102 on client machines.
Mail received at the mail server is typically processed based on a recipient address identified within the electronic mail. Once the recipient is known, the mail server assigns a unique identifier to the piece of electronic mail, which is common in, for example, the IMAP4 standard. This identifier is unique among each mail user's inbox, such that each message in the inbox has a different identifier. These unique identifiers are typically assigned according to known algorithms. In this way, the mail server is able to provide electronic mail storage and management for a large population of authorized electronic mail clients.
Each user then may utilize a mail client to retrieve electronic mail from the mail server. The mail client may have only periodic access to the Internet, or other external networks and public data communications networks. The mail client may maintain local copies of selected electronic mails corresponding to the user. The mail client accesses the server to retrieve mail from the inbox. This is accomplished by providing authorization credentials to the authorized mail box. This may be repeated periodically to allow the mail client to download and/or copy newly received electronic mails into local storage. This is typically known as “polling”.
Typically, polling involves the mail client requesting a full listing of all the email header information. This full listing of all headers is then compared to the local storage record of the client. If there are any discrepancies, the client may then initiate data transfer(s) to synchronize the mail client's record with the mail server's record. This may include downloading new mail items that exist on the mail server but not on the mail client, as well as deleting old mail items that exist on the mail client but no longer exist on the mail server (for example, if an email has been recalled).
Each such polling event results in a large amount of data transferring between the mail server and the mail client. Furthermore, each polling event requires small but significant computational resources from the mail server. Frequent polling is required to ensure a short delay between the time when the mail server receives new mail and the time when the mail client is aware of the arrival of new mail. However, frequent polling increases the traffic capacity requirement of the network, as well as the computational resource usage on the mail server.
On the mail server side, when new mail is received, it must first check the recipient address to identify whether the client has set up any sort of server-initiated-notification preference for new mail arrival. If so, then the mail server must configure the necessary notification message containing the relevant information about the new mail item and transmit it to the associated mail client. Upon receipt of this notification, the mail client initiates the necessary actions based on the information provided in the notification. Some of the possible actions may include, but are not limited to, downloading the new message, ignoring the new message, deleting the new message, and forwarding the new message. While this can provide near-instantaneous notification of new email, the establishment of an ongoing session between the mail server and the mail client consumes significant computing resources at the mail server. A server-initiated-notification message must be sent on the arrival of each and every new mail item. For users who receive frequent mailings, this can be a significant load on mail server resources.
Additionally, these techniques are an inefficient use of data communications resources for most e-mail users. Each data message transmitted incurs a fixed overhead within the data communications network. When each message only contains information about a single new mail item, the percentage overhead is significantly higher than if a single data message contains information about multiple new mail items. Furthermore, the user may not require the immediacy of server-initiated-notification at all times.
What is needed is a solution that allows the prompt notification of new mail arrival while minimizing unnecessary loading of mail server and network resources.